VoIP kills network?

[andyfram]

I have 4 branches that are now using VoIP Gateway cards.
One branch has a TDA600 on a T1 - works fine.
The second has a TDA200 on a T1 - works fine.
The third has a TDA100 on DSL - works fine.
The fourth has a TDA100 on DSL through AT&T.

In the fourth branch, as long as the VoIP Gateway card is connected, the entire network dies every few hours until the DSL modem is reset. When the VoIP card is removed from the network, the network has been fine for days.

The line quality is good, VoIP calls sound great, and there is very little bandwidth usage. Is there something about AT&T or DSL that might cause a conflict? One of the users in the fourth branch has said that at home, his AT&T DSL connection also drops whenever he makes an outbound call using AT&Ts VoIP service.

 

[cwc3]

some routers have a auto reset option
you should turn it on untill you solve the problem

 

[andyfram]

Thanks for the tip, but it looks like this particular model modem doesn't have an auto restart feature.

We did find out that the network dies after making an outbound intercom call using VoIP.

The third branch listed in post 1 is also using DSL, but does not seem to be experiencing this problem.

 

[cwc3]

same router ? do you have multitech pathfinders set up?
do you have the right ports open?

 

[DavidCT]

andyfram,

What router/firewall are you using? Are your sites connected by VPN or did you open ports?

Look for two settings:

1. MTU on the WAN port. Most DSL circuits are 1492. Most routers default to 1500 (which is what works for a T1).

2. If you are connected by VPN, look for an option specific to VPN such as "Don't Fragment". Turn this off if it's on.

 

[andyfram]

We are trying it without VPN at this time to rule out any firewall issues.

The MTU is set to 1500 on the Netopia 3346N DSL modem - revision 7 firmware in the problem branch. The next hop however is set at 1492 and cannot be changed.

Running the modem's diagnostic tests show everything is OK, except that the "hearbeat" service is disabled...and I can't find a way to enable it.